WO2018047565A1

WO2018047565A1 - Sulfide solid electrolyte

Info

Publication number: WO2018047565A1
Application number: PCT/JP2017/028782
Authority: WO
Inventors: 恒太寺井; 太宇都野; 孝梅木; 中川　將; 展史山口
Original assignee: 出光興産株式会社
Priority date: 2016-09-12
Filing date: 2017-08-08
Publication date: 2018-03-15
Also published as: US20210075057A1; EP3511949B1; US11271246B2; TW201817075A; EP3511949A1; TW201817074A; JP6679737B2; EP3511949A4; US20190140314A1; JP7178452B2; JP6679736B2; US20230282876A1; US10374253B2; JP7536842B2; CN109690697B; KR20240026252A; KR102527435B1; CN109690696B; US20190140313A1; KR102641046B1

Abstract

A sulfide solid electrolyte which contains lithium, phosphorus, sulfur and two or more elements X selected from among halogen elements, while having an argyrodite crystal structure, and wherein the molar ratio b (S/P) of the sulfur to the phosphorus and the molar ratio c (X/P) of the elements X to the phosphorus satisfy formula (1). 0.23 < c/b < 0.57 (1)

Description

Sulfide solid electrolyte

The present invention relates to a sulfide solid electrolyte, an electrode mixture, and a lithium ion battery.

In recent years, with the rapid spread of information-related equipment and communication equipment such as personal computers, video cameras, and mobile phones, development of batteries that are used as power sources is regarded as important. Among these batteries, lithium ion batteries are attracting attention from the viewpoint of high energy density.

Currently marketed lithium-ion batteries use electrolytes containing flammable organic solvents, so safety devices that prevent temperature rise during short circuits and improvements in structure and materials to prevent short circuits Is required. In contrast, a lithium ion battery that uses a solid electrolyte by changing the electrolyte to a solid electrolyte does not use a flammable organic solvent in the battery, so the safety device can be simplified, and manufacturing costs and productivity can be reduced. It is considered excellent.

A sulfide solid electrolyte is known as a solid electrolyte used in a lithium ion battery. Various crystal structures of the sulfide solid electrolyte are known, and one of them is an Argyrodite type crystal structure (Patent Documents 1 to 5, Non-Patent Documents 1 to 3). Non-Patent

Documents

4 and 5 disclose a solid electrolyte having a composition of Li ₆ PS ₅ X and containing chlorine and bromine in a specific ratio. Some argilodite-type crystal structures have high lithium ion conductivity. However, further improvements in ionic conductivity are desired. In general, sulfide-based solid electrolytes have a problem that hydrogen sulfide may be generated by reacting with moisture in the atmosphere.

Special table 2010-540396 International Publication WO2015 / 011937 International Publication WO2015 / 012042 JP 2016-24874 A International Publication WO2016 / 104702

One of the objects of the present invention is to provide a novel sulfide solid electrolyte having higher ionic conductivity.
Another object of the present invention is to provide an excellent novel sulfide solid electrolyte that suppresses the amount of hydrogen sulfide generated.

According to one embodiment of the present invention, the lithium includes phosphorus, sulfur, sulfur, and two or more elements X selected from halogen elements, includes an aldilodite-type crystal structure, and the molar ratio of sulfur to phosphorus There is provided a sulfide solid electrolyte in which the molar ratio c (X / P) of b (S / P) and element X to phosphorus satisfies the following formula (1).
0.23 <c / b <0.57 (1)
Moreover, according to one Embodiment of this invention, the electrode compound material containing the said sulfide solid electrolyte and an active material is provided.
According to an embodiment of the present invention, there is provided a lithium ion battery including at least one of the sulfide solid electrolyte and the electrode mixture.

According to one embodiment of the present invention, a sulfide solid electrolyte having high ionic conductivity can be provided.
Moreover, according to one Embodiment of this invention, the sulfide solid electrolyte which suppressed the amount of hydrogen sulfide generation can be provided.

2 is an X-ray diffraction pattern of the sulfide solid electrolyte obtained in Example 1. FIG. 4 is an X-ray diffraction pattern of the sulfide solid electrolyte obtained in Example 4. It is the top view fractured | ruptured at the center of the rotating shaft of an example of the multi-axis kneader used for manufacture of sulfide solid electrolyte. It is the top view fractured | ruptured perpendicularly with respect to this rotating shaft of the part in which the paddle of a rotating shaft is provided of an example of the multi-axis kneader used for manufacture of sulfide solid electrolyte. It is explanatory drawing of the apparatus used for hydrogen sulfide generation amount evaluation of sulfide solid electrolyte.

The sulfide solid electrolyte according to one embodiment of the present invention includes lithium, phosphorus, sulfur, and two or more elements X selected from halogen elements. Further, it includes an aldilodite-type crystal structure, and the molar ratio b (S / P) of sulfur to phosphorus and the molar ratio c (X / P) of element X to phosphorus satisfy the following formula (1).
0.23 <c / b <0.57 (1)
The molar ratio of the element X is the sum of all halogen elements contained in the sulfide solid electrolyte. For example, when the element X is two types of halogen x1 and x2, the molar ratio c of the element X is (x1 + x2) / P.

C / b in the above formula (1) is the molar ratio of the halogen element to sulfur in the sulfide solid electrolyte. In a sulfide solid electrolyte containing an aldilodite-type crystal structure and containing two or more types of halogen elements, the molar ratio of the halogen element to sulfur is within the range of the formula (1), whereby the ionic conductivity of the sulfide solid electrolyte Becomes higher.

In general, various crystalline components and amorphous components are mixed in the sulfide solid electrolyte. Part of the halogen (element X) introduced as a constituent element of the sulfide solid electrolyte forms an aldilodite-type crystal structure, and other halogen forms a crystal structure other than the aldilodite-type crystal structure and an amorphous component. . Moreover, the case where it is contained in the residual raw material is also considered.
The aldilodite-type crystal structure is a structure in which PS ₄ ^3- structure is the main unit structure of the skeleton, and S and halogen surrounded by Li occupy the surrounding sites. A general argilodite type crystal structure is a crystal structure represented by a space group F-43M. No. in the database of International Tables for Crystallography Volume G: Definition and exchange of crystallographic data (ISBN: 978-1-4020-3138-0). 216 is a crystal structure. No. In the crystal structure shown in 216, there are 4a sites and 4d sites around the PS ₄ ^3- structure. Elements with large ionic radii tend to occupy 4a sites, and elements with small ionic radii occupy 4d sites. easy. In the present embodiment, it is presumed that a larger amount of halogen can be occupied at both the 4a site and the 4d site by including an appropriate amount of two or more types of halogen in the sulfide solid electrolyte. As a result, the inventors have found a novel sulfide solid electrolyte containing a novel argilodite type crystal structure with a high halogen content.

In the unit cell of the argilodite type crystal structure, there are a total of 8 4a sites and 4d sites. An increase in the amount of halogen that occupies sites in the argilodite-type crystal structure means that the amount of S that occupies sites in the aldilodite-type crystal structure is relatively reduced. Halogen having a valence of −1 is weaker in attracting Li than S having a valence of −2. Also, the number of attracted Li is small. Therefore, the density of Li in the vicinity of the site is reduced, and Li is easy to move. Therefore, it is considered that the ionic conductivity of the argilodite type crystal structure is increased.

Examples of the halogen element include F, Cl, Br, and I.
Since the effect of improving the ionic conductivity is greater, the above formula (1) is preferably 0.25 ≦ c / b ≦ 0.43, and 0.30 ≦ c / b ≦ 0.41. It is more preferable.

In this application, the molar ratio and composition of each element in the sulfide solid electrolyte are values measured by an ICP emission analysis method except for special circumstances such as difficulty in analysis. The measuring method of ICP emission spectrometry is described in the examples.
The molar ratio of each element can be controlled by adjusting the content of each element in the raw material.

The sulfide solid electrolyte of the present embodiment includes an argilodite type crystal structure. The inclusion of an aldilodite crystal structure can be confirmed by having diffraction peaks at 2θ = 25.2 ± 0.5 deg and 29.7 ± 0.5 deg in powder X-ray diffraction measurement using CuKα rays.
The diffraction peaks at 2θ = 25.2 ± 0.5 deg and 29.7 ± 0.5 deg are peaks derived from the aldilodite crystal structure.
The diffraction peaks of the aldilodite type crystal structure are, for example, 2θ = 15.3 ± 0.5 deg, 17.7 ± 0.5 deg, 31.1. It may appear at ± 0.5 deg, 44.9 ± 0.5 deg, 47.7 ± 0.5 deg. The sulfide solid electrolyte of the present embodiment may have these peaks.

In the present application, the position of the diffraction peak is determined as A ± 0.5 deg or A ± 0.4 deg when the median is A, but is preferably A ± 0.3 deg. For example, in the case of the diffraction peak of 2θ = 25.2 ± 0.5 deg described above, the median value A is 25.2 deg, and preferably exists in the range of 2θ = 25.2 ± 0.3 deg. The same applies to the determination of all other diffraction peak positions in the present application.

In the present embodiment, the type of the element X contained in the sulfide solid electrolyte is preferably 2 or more, 4 or less, more preferably 2 or 3 types, and more preferably 2 types.
At least one of the elements X is preferably chlorine or bromine, and the element X preferably contains chlorine and bromine.
When at least one of the elements X is chlorine, it is preferable to satisfy the following formula (2).
0.25 <X _Cl <1 (2)
(In the formula, _XCl represents the molar ratio of chlorine to element X.)
By satisfy | filling Formula (2), ionic conductivity becomes higher. Since a conduction path is formed by mixing chlorine with other ions, the formula (2) is preferably 0.30 ≦ X _Cl ≦ 0.95, and 0.35 ≦ X _Cl ≦ 0.95. It is more preferable that
It is presumed that there is a region with higher ion conductivity as described above depending on the type and combination of the element X.
In the sulfide solid electrolyte of the present embodiment, when 0.30 ≦ c / b ≦ 0.41 and 0.25 <X _Cl <1, the ion conductivity may be increased to 6.9 mS / cm or more. it can. In the case of 0.30 ≦ c / b ≦ 0.41 and 0.35 ≦ X _Cl ≦ 0.95, the ionic conductivity can be further increased to 9 mS / cm to 13 mS / cm.

In the sulfide solid electrolyte of the present embodiment, the molar ratio c (X / P) of element X to phosphorus is preferably greater than 1.1 and not greater than 1.9, and not less than 1, 4 and not greater than 1.8. More preferably. By making molar ratio c into the said range, the improvement effect of the ionic conductivity of sulfide solid electrolyte becomes higher.

The sulfide solid electrolyte of this embodiment includes a molar ratio a (Li / P) of lithium to phosphorus, a molar ratio b (S / P) of sulfur to phosphorus, and a molar ratio c (X / P) of element X to phosphorus. In this case, it is preferable that the following formulas (A) to (C) are satisfied.
5.0 ≦ a ≦ 7.5 (A)
6.5 ≦ a + c ≦ 7.5 (B)
0.5 ≦ ab ≦ 1.5 (C)
(In the formula, b> 0 and c> 0 are satisfied.)
By satisfying the above formulas (A) to (C), an aldilodite crystal structure is easily formed.

In the formula (B), 6.6 ≦ a + c ≦ 7.4 is preferable, and 6.7 ≦ a + c ≦ 7.3 is more preferable.
In the above formula (C), 0.6 ≦ ab ≦ 1.3 is preferable, and 0.7 ≦ ab ≦ 1.3 is more preferable.

In addition to the lithium, phosphorus, sulfur, and element X, elements such as Si, Ge, Sn, Pb, B, Al, Ga, As, Sb, and Bi may be included. Further, a chalcogen element (oxygen (O), selenium (Se), tellurium (Te), or the like) may be included. When the sulfide solid electrolyte contains one or more elements M selected from the group consisting of Si, Ge, Sn, Pb, B, Al, Ga, As, Sb, and Bi, the above (A) to (C) The molar ratio of each element is the molar ratio with respect to the total of the element M and phosphorus. For example, the molar ratio a (Li / P) of lithium to phosphorus is Li / (P + M).

The sulfide solid electrolyte of the present embodiment preferably satisfies, for example, a composition represented by the following formula (3).
Li _a (P _1−α M _α ) S _b X _c (3)
Wherein M is one or more elements selected from the group consisting of Si, Ge, Sn, Pb, B, Al, Ga, As, Sb and Bi, and X is F, Cl, Br and I Two or more elements selected from the group consisting of: a to c satisfy the following formulas (A) to (C), and α is 0 ≦ α ≦ 0.3.
5.0 ≦ a ≦ 7.5 (A)
6.5 ≦ a + c ≦ 7.5 (B)
0.5 ≦ ab ≦ 1.5 (C)
(In the formula, b> 0 and c> 0 are satisfied.)

X in the formula (3) represents two or more elements selected from the group consisting of F, Cl, Br and I (x ₁ ,..., X _n : n is an integer of 2 or more and 4 or less). By incorporating a halogen element into the argilodite type crystal structure, ion conductivity is increased. X is preferably composed of two (x ₁ , x ₂ ) or three (x ₁ , x ₂ , x ₃ ) elements, and more preferably composed of two elements. The molar ratio of each element is not particularly limited, but when chlorine is included, it is preferable to satisfy the above formula (2).
α is preferably 0.

The above-mentioned molar ratios and compositions of the elements are not the molar ratios and compositions of the input materials used in the production, but the products in the sulfide solid electrolyte. The molar ratio of each element can be controlled by adjusting the content of each element in the raw material, for example.

In the powder X-ray diffraction using CuKα rays, the sulfide solid electrolyte of the present embodiment preferably does not have a diffraction peak of lithium halide or satisfies the following formula (4).
_{_{0 <I A / I B <}} 0.1 (4)
(Wherein, _{I A} represents the intensity of the diffraction peak of lithium halide, _{I B} represents the intensity of the diffraction peak of 2θ = 25.2 ± 0.5deg.)
The above formula (4) represents that the amount of lithium halide is relatively small as compared with the aldilodite crystal structure. The presence of lithium halide means that excessive halogen exists in the solid electrolyte due to a cause such as a case where the content of halogen in the raw material is high. Incidentally, for example, _{I A} is when lithium halide is LiCl assumed to be the intensity of a diffraction peak of 2 [Theta] = 50.3 ± 0.5 deg, _{I A} is 2 [Theta] = 46.7 ± if a LiBr assumed to be the intensity of the diffraction peak of 0.5 deg, in the case of LiF is assumed the _{I a} is the intensity of a diffraction peak of 2θ = 45.0 ± 0.5deg, the _{I a} when a LiI assumed to be the intensity of a diffraction peak of 2θ = 42.4 ± 0.5deg, _{I a} is the sum of the intensities of the diffraction peaks of a lithium halide. Equation (4) _is 0 _<more preferably _I is A / I B _<0.05, more preferably 0 _<I A / I B <0.03.

In addition, the sulfide solid electrolyte of this embodiment has a diffraction peak (algirodite type crystal structure) at 2θ = 17.6 ± 0.4 deg and 2θ = 18.1 ± 0.4 deg in powder X-ray diffraction using CuKα rays. It is preferable that the following formula (5) is satisfied.
_{_{0 <I C / I D <}} 0.05 (5)
(In the formula, I _C represents the intensity of the diffraction peak of 2θ = 17.6 ± 0.4 deg and 2θ = 18.1 ± 0.4 deg, although it is not the diffraction peak of the argilodite crystal structure, and _ID is 2θ. = Represents the intensity of a diffraction peak of 29.7 ± 0.5 deg.)

Since the crystal structure specified by I _C (hereinafter referred to as Li ₃ PS ₄ crystal structure) has low ionic conductivity, the ionic conductivity of the solid electrolyte is lowered. The above formula (5) represents that the amount of the Li ₃ PS ₄ crystal structure is relatively small as compared with the aldilodite crystal structure. In Formula (5), 0 <I _C / _ID <0.03 is more preferable, and 0 <I _C / _ID <0.02 is more preferable.
Note that either 2θ = 17.6 ± 0.4 deg or 2θ = 18.1 ± 0.4 deg usually cannot be measured because it overlaps with the diffraction peak of the aldirodite crystal structure having a relatively strong peak intensity. Therefore, 2θ = 17.6 ± 0.4 deg and 2θ = 18.1 ± 0.4 deg which is not a diffraction peak of the argilodite type crystal structure are usually weak in intensity of these two observed peaks. Means better. In some cases, the background or noise of the measured intensity S / N ratio is observed like a peak. In such a case, it is needless to say that Expression (5) is satisfied even if these are assumed to be _ID .

In addition, in the powder X-ray diffraction using CuKα rays, the sulfide solid electrolyte of the present embodiment has or does not have a diffraction peak other than the diffraction peak of the aldilodite crystal structure, and satisfies the following formula. preferable.
0 <I _E / _ID <0.1
(Wherein, _{I E} represents the intensity of diffraction peaks other than the diffraction peaks of Arujirodaito type crystal structure, _{I D} represents the intensity of the diffraction peak of 2θ = 29.7 ± 0.5deg.)
In the above formula, 0 <I _E / _ID <0.05 is more preferable, and 0 <I _E / _ID <0.03 is more preferable.

The sulfide solid electrolyte of the present embodiment is a production method having a step of producing an intermediate by reacting a mixture of raw materials described later by applying mechanical stress, and a step of crystallizing the intermediate by heat treatment Can be produced.

The raw material to be used is a combination of two or more compounds or a single element containing, as a whole, two or more elements X selected from lithium, phosphorus, sulfur and halogen elements, which are essential elements of the sulfide solid electrolyte to be produced To use.

Examples of the raw material containing lithium include lithium compounds such as lithium sulfide (Li ₂ S), lithium oxide (Li ₂ O), and lithium carbonate (Li ₂ CO ₃ ), and lithium metal alone. Among these, lithium compounds are preferable, and lithium sulfide is more preferable.
Although the said lithium sulfide can be used without a restriction | limiting especially, a highly purified thing is preferable. Lithium sulfide can be produced, for example, by the methods described in JP-A-7-330312, JP-A-9-283156, JP-A-2010-163356, and JP-A-2011-84438.
Specifically, lithium hydroxide and hydrogen sulfide are reacted at 70 ° C. to 300 ° C. in a hydrocarbon-based organic solvent to produce lithium hydrosulfide, and then the reaction solution is desulfurized by dehydrosulfurization. Lithium can be synthesized (Japanese Patent Laid-Open No. 2010-163356).
In addition, lithium hydroxide and hydrogen sulfide are reacted at 10 ° C. to 100 ° C. in an aqueous solvent to produce lithium hydrosulfide, and then this reaction solution is dehydrosulfurized to synthesize lithium sulfide (special feature). No. 2011-84438).

Examples of the raw material containing phosphorus include phosphorus sulfide such as diphosphorus trisulfide (P ₂ S ₃ ) and diphosphorus pentasulfide (P ₂ S ₅ ), phosphorus compounds such as sodium phosphate (Na ₃ PO ₄ ), and Examples include phosphorus alone. Among these, phosphorus sulfide is preferable and diphosphorus pentasulfide (P ₂ S ₅ ) is more preferable. Phosphorus compounds such as diphosphorus pentasulfide (P ₂ S ₅ ) and simple phosphorus can be used without particular limitation as long as they are industrially produced and sold.

As a raw material containing the element X, it is preferable that the halogen compound represented by following formula (6) is included, for example.
M _l -X _m (6)

In formula (6), M is sodium (Na), lithium (Li), boron (B), aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), germanium (Ge), arsenic (As), selenium (Se), tin (Sn), antimony (Sb), tellurium (Te), lead (Pb), bismuth (Bi), or a combination of these elements with oxygen and sulfur Lithium (Li) or phosphorus (P) is preferable, and lithium (Li) is more preferable.
X is a halogen element selected from fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).
L is an integer of 1 or 2, and m is an integer of 1 to 10. When m is an integer of 2 to 10, that is, when there are a plurality of Xs, Xs may be the same or different. For example, in SiBrCl ₃ described later, m is 4, and X is composed of different elements such as Br and Cl.

Specific examples of the halogen compound represented by the above formula (6) include sodium halides such as NaI, NaF, NaCl, and NaBr; lithium halides such as LiF, LiCl, LiBr, and LiI; BCl ₃ , BBr ₃ Boron halides such as Al ₃ , BI ₃ ; aluminum halides such as AlF ₃ , AlBr ₃ , AlI ₃ , AlCl ₃ ; SiF ₄ , SiCl ₄ , SiCl ₃ , Si ₂ Cl ₆ , SiBr ₄ , SiBrCl ₃ , SiBr ₂ Cl ₂ , SiI ₄ and halogenated _{_{_{_{silicon; PF 3, PF 5, PCl}}}} 3, PCl 5, POCl 3, PBr 3, POBr 3, PI 3, P 2 Cl 4, P 2 I 4 halogenated such as phosphorus; SF ₂ , SF ₄ , SF ₆ , S ₂ F ₁₀ , SCl ₂ , S ₂ Cl ₂ , S ₂ Br _2, etc. Sulfur; germanium halides such as GeF ₄ , GeCl ₄ , GeBr ₄ , GeI ₄ , GeF ₂ , GeCl ₂ , GeBr ₂ , GeI ₂ ; halogenated arsenic such as AsF ₃ , AsCl ₃ , AsBr ₃ , AsI ₃ , AsF ₅ _{_{_{; SeF 4, SeF 6, SeCl}}} 2, SeCl 4, Se 2 Br 2, SeBr 4 halogenated such as _{_{_{selenium; SnF 4, SnCl 4, SnBr}}} 4, SnI 4, SnF 2, SnCl 2, SnBr 2, SnI 2 , etc. Tin halides of SbF ₃ , SbCl ₃ , SbBr ₃ , SbI ₃ , SbF ₅ , SbCl _5, etc .; TeF ₄ , Te ₂ F ₁₀ , TeF ₆ , TeCl ₂ , TeCl ₄ , TeBr ₂ , TeBr ₂ halogenated tellurium such as TeI _{_{_4;}} PbF _4, PbCl ₄ _{_{_{PbF 2, PbCl 2, PbBr 2}}} , PbI 2 , etc. lead halide _{_{_{of; BiF 3, BiCl 3, BiBr}}} 3, BiI 3 halogenated bismuth, etc., and the like.

Among them, lithium halides such as lithium chloride (LiCl), lithium bromide (LiBr), and lithium iodide (LiI), phosphorus pentachloride (PCl ₅ ), phosphorus trichloride (PCl ₃ ), phosphorus pentabromide (PBr ₅₎ ) And phosphorus halides such as phosphorus tribromide (PBr ₃ ) are preferred. Among these, lithium halides such as LiCl, LiBr, and LiI and PBr ₃ are preferable, lithium halides such as LiCl, LiBr, and LiI are more preferable, and LiCl and LiBr are more preferable.
A halogen compound may be used individually from said compound, and may be used in combination of 2 or more type. That is, at least one of the above compounds can be used.

In the present embodiment, the raw material contains a lithium compound, a phosphorus compound, and two or more halogen compounds, and at least one of the lithium compound and the phosphorus compound preferably contains a sulfur element. A combination of the above lithium halides is more preferable, and a combination of lithium sulfide, diphosphorus pentasulfide, and two or more lithium halides is still more preferable.
For example, when lithium sulfide, diphosphorus pentasulfide, or two or more types of lithium halides are used as the raw material for the sulfide solid electrolyte of the present embodiment, the molar ratio of the input raw materials is changed to lithium sulfide: phosphorous pentasulfide. : Total of two or more lithium halides = 30 to 60:10 to 25:15 to 50

In the present embodiment, mechanical stress is applied to the raw material to cause a reaction to obtain an intermediate. Here, “applying mechanical stress” means mechanically applying a shearing force, an impact force or the like. Examples of the means for applying mechanical stress include a pulverizer such as a planetary ball mill, a vibration mill, and a rolling mill, and a kneader.
In the prior art (for example, Patent Document 2), pulverization and mixing are performed to such an extent that the crystallinity of the raw material powder can be maintained. On the other hand, in the present embodiment, it is preferable to apply a mechanical stress to the raw material to cause a reaction to obtain an intermediate containing a glass component. That is, by mechanical stress stronger than in the prior art, at least a part of the raw material powder is pulverized and mixed until it cannot maintain crystallinity. As a result, a PS ₄ structure, which is a basic skeleton of an aldilodite crystal structure, can be produced at the intermediate stage, and halogen can be highly dispersed. As a result, when the heat treatment in the next step is performed, the halogen is easily incorporated into the aldilodite crystal structure when the aldilodite crystal structure, which is a stable phase, is obtained. Since no through different phases in each area, low ionic conducting phase such as Li ₃ PS ₄ crystal structure is estimated to be less likely to occur. Thereby, it is estimated that the sulfide solid electrolyte of this invention expresses high ionic conductivity.
Note that the presence of the glass (amorphous) component in the intermediate can be confirmed by the presence of a broad peak (halo pattern) due to the amorphous component in the XRD measurement.
Further, the sulfide solid electrolyte of the present embodiment has high mass productivity because it is not necessary to heat the raw material at 550 ° C. for 6 days as in Patent Document 1.

As the conditions for pulverization and mixing, for example, when a planetary ball mill is used as the pulverizer, the rotational speed may be several tens to several hundreds of revolutions / minute, and the treatment may be performed for 0.5 hours to 100 hours. More specifically, in the case of the planetary ball mill used in the examples of the present application (manufactured by Fritsch: model number P-7), the rotational speed of the planetary ball mill is preferably 350 rpm to 400 rpm, more preferably 360 rpm to 380 rpm.
For example, when a zirconia ball is used as the grinding media, the diameter is preferably 0.2 to 20 mm.

The intermediate produced by pulverization and mixing is heat-treated. The heat treatment temperature is preferably 350 to 650 ° C., more preferably 360 to 500 ° C., and more preferably 380 to 450 ° C. When the heat treatment temperature is slightly lower than the conventional temperature, the halogen contained in the aldilodite type crystal structure tends to increase.
The atmosphere of the heat treatment is not particularly limited, but is preferably not an atmosphere of hydrogen sulfide but an inert gas atmosphere such as nitrogen or argon. By suppressing the substitution of free halogen in the crystal structure with sulfur, the amount of halogen in the crystal structure can be increased, and as a result, the ionic conductivity of the resulting sulfide solid electrolyte is estimated to be improved. .

When a kneader is used as the means for applying the mechanical stress, the kneader is not particularly limited, but a multi-axis kneader having two or more shafts is preferable from the viewpoint of easy production.

The multi-axis kneader includes, for example, a casing, and two or more rotating shafts that are arranged so as to penetrate the casing in the longitudinal direction and are provided with paddles (screws) along the axial direction. The other configuration is not particularly limited as long as it is provided with a raw material supply port at one end in the longitudinal direction and a discharge port at the other end, and two or more rotational movements interact to generate mechanical stress. Absent. By rotating two or more rotary shafts provided with paddles of such a multi-axis kneader, two or more rotary motions can interact to generate mechanical stress along the rotary shaft. Thus, the mechanical stress can be applied to the raw material moving in the direction from the supply port to the discharge port to cause a reaction.

A preferred example of the multi-screw kneader that can be used in the present invention will be described with reference to FIGS. FIG. 3 is a plan view broken at the center of the rotating shaft of the kneader, and FIG. 4 is a plan view broken perpendicularly to the rotating shaft of the portion where the paddle of the rotating shaft is provided.
The multi-axis kneader shown in FIG. 3 includes a casing 1 having a supply port 2 at one end and a discharge port 3 at the other end, and two

rotating shafts

4 a and 4 b so as to penetrate in the longitudinal direction of the casing 1. It is a shaft kneader.

Paddles

5a and 5b are provided on the

rotary shafts

4a and 4b, respectively. The raw material enters the casing 1 from the supply port 2 and is reacted by applying mechanical stress in the

paddles

5 a and 5 b, and the obtained reaction product is discharged from the discharge port 3.

The number of the rotating shafts 4 is not particularly limited as long as it is two or more. In consideration of versatility, the number of the rotating shafts 4 is preferably 2 to 4, and more preferably 2. Further, the rotation shafts 4 are preferably parallel axes that are parallel to each other.
The paddle 5 is provided on the rotating shaft for kneading the raw materials, and is also referred to as a screw. There are no particular restrictions on the cross-sectional shape, and as shown in FIG. 4, in addition to a substantially triangular shape in which each side of the equilateral triangle is a convex arc, a circular shape, an elliptical shape, a substantially rectangular shape, etc. Based on the shape, a shape having a notch in part may be used.

When a plurality of paddles are provided, as shown in FIG. 4, each paddle may be provided on the rotating shaft at a different angle. Further, when trying to obtain the effect of kneading, the paddle may be a mesh type.
The rotational speed of the paddle is not particularly limited, but is preferably 40 to 300 rpm, more preferably 40 to 250 rpm, and even more preferably 40 to 200 rpm.

The multi-screw kneader may be provided with a screw 6 on the supply port 2 side as shown in FIG. 3 in order to feed the raw material into the kneader without any delay, and the reactant obtained through the paddle 5 is a casing. In order not to stay inside, a reverse screw 7 may be provided on the discharge port 3 side as shown in FIG.
A commercially available kneader can also be used as the multiaxial kneader. As a commercially available multi-axis kneader, for example, KRC kneader (manufactured by Kurimoto Steel Works) and the like can be mentioned.

The kneading time of the raw material varies depending on the kind of element constituting the sulfide solid electrolyte to be obtained, the composition ratio, and the temperature at the time of reaction, and may be adjusted as appropriate, preferably 5 minutes to 50 hours, more preferably 10 Min to 15 hours, more preferably 1 to 12 hours.
The kneading temperature of the raw material varies depending on the kind of element constituting the sulfide solid electrolyte to be obtained, the composition ratio, and the reaction time, and may be adjusted as appropriate, preferably 0 ° C. or higher, more preferably 25 ° C. or higher. More preferably, it is 100 ° C. or higher, most preferably 250 ° C. or higher. The higher the temperature, the more it becomes possible to precipitate an argilodite type crystal structure at the time of kneading. If it is 350 degreeC or more, it will be thought that an aldilodite type crystal structure precipitates more easily. The upper limit of the kneading temperature may be such that the generated aldilodite crystal structure is not decomposed, that is, 650 ° C. or lower.

The intermediate that has come out from the discharge port of the multi-screw kneader may be supplied again from the supply port according to the degree of progress of the reaction, and the reaction may be further advanced. The degree of progress of the reaction can be grasped by the increase or decrease of the peak derived from the raw material of the obtained intermediate.

A sulfide solid electrolyte is obtained by heat-treating the intermediate obtained by kneading. The heat treatment temperature is preferably 350 to 650 ° C., more preferably 360 to 500 ° C., and more preferably 380 to 450 ° C. The atmosphere of the heat treatment is not particularly limited, but is preferably not an atmosphere of hydrogen sulfide but an inert gas atmosphere such as nitrogen or argon.

The sulfide solid electrolyte of the present invention can be used for a solid electrolyte layer such as a lithium ion secondary battery, a positive electrode, a negative electrode, and the like.

[Electrode compound]
The electrode mixture of one embodiment of the present invention includes the above-described sulfide solid electrolyte of the present invention and an active material. Or it manufactures with the sulfide solid electrolyte of this invention. When a negative electrode active material is used as the active material, a negative electrode mixture is obtained. On the other hand, when a positive electrode active material is used, it becomes a positive electrode mixture.

-Negative electrode compound material A negative electrode compound material is obtained by mix | blending a negative electrode active material with the sulfide solid electrolyte of this invention.
As the negative electrode active material, for example, a carbon material, a metal material, or the like can be used. Among these, a complex composed of two or more kinds can also be used. Moreover, a negative electrode active material developed in the future can also be used.
Moreover, it is preferable that the negative electrode active material has electronic conductivity.
Examples of carbon materials include graphite (eg, artificial graphite), graphite carbon fiber, resin-fired carbon, pyrolytic vapor-grown carbon, coke, mesocarbon microbeads (MCMB), furfuryl alcohol resin-fired carbon, polyacene, pitch-based carbon. Examples thereof include fibers, vapor-grown carbon fibers, natural graphite, and non-graphitizable carbon.
Examples of the metal material include simple metals, alloys, and metal compounds. Examples of the metal simple substance include metal silicon, metal tin, metal lithium, metal indium, and metal aluminum. Examples of the alloy include an alloy containing at least one of silicon, tin, lithium, indium, and aluminum. Examples of the metal compound include metal oxides. Examples of the metal oxide include silicon oxide, tin oxide, and aluminum oxide.

The mixing ratio of the negative electrode active material and the solid electrolyte is preferably negative electrode active material: solid electrolyte = 95 wt%: 5 wt% to 5 wt%: 95 wt%, 90 wt%: 10 wt% to 10 wt%: 90 wt%. %, More preferably 85% by weight: 15% by weight to 15% by weight: 85% by weight.
When there is too little content of the negative electrode active material in a negative electrode compound material, an electrical capacity will become small. In addition, when the negative electrode active material has electronic conductivity and does not contain a conductive aid or contains only a small amount of a conductive aid, the electronic conductivity (electron conduction path) in the negative electrode is reduced, and the rate It is considered that there is a possibility that the characteristics may be lowered, or the utilization rate of the negative electrode active material may be reduced, and the electric capacity may be reduced. On the other hand, if the content of the negative electrode active material in the negative electrode mixture is too large, the ion conductivity (ion conduction path) in the negative electrode is lowered, the rate characteristics may be lowered, the utilization rate of the negative electrode active material is lowered, and We think that capacity may decrease.

The negative electrode mixture can further contain a conductive additive.
When the negative electrode active material has low electronic conductivity, it is preferable to add a conductive additive. The conductive auxiliary agent only needs to have conductivity, and its electronic conductivity is preferably 1 × 10 ³ S / cm or more, more preferably 1 × 10 ⁵ S / cm or more.
Specific examples of conductive aids are preferably carbon materials, nickel, copper, aluminum, indium, silver, cobalt, magnesium, lithium, chromium, gold, ruthenium, platinum, beryllium, iridium, molybdenum, niobium, osnium, rhodium, A substance containing at least one element selected from the group consisting of tungsten and zinc, and more preferably a carbon simple substance having a high conductivity, or a carbon material other than simple carbon; nickel, copper, silver, cobalt, magnesium, lithium, ruthenium , Gold, platinum, niobium, osnium or rhodium, simple metals, mixtures or compounds.
Specific examples of carbon materials include carbon blacks such as ketjen black, acetylene black, denka black, thermal black, and channel black; graphite, carbon fiber, activated carbon, and the like. These may be used alone or in combination of two or more. Is possible. Among these, acetylene black, denka black, and ketjen black having high electron conductivity are preferable.

In the case where the negative electrode mixture contains a conductive additive, the content of the conductive additive in the mixed material is preferably 1 to 40% by mass, more preferably 2 to 20% by mass. If the content of the conductive additive is too small, the electron conductivity of the negative electrode may be reduced to lower the rate characteristics, and the utilization rate of the negative electrode active material may be reduced, resulting in a decrease in electric capacity. On the other hand, when there is too much content of a conductive support agent, the quantity of a negative electrode active material and / or the quantity of a solid electrolyte will decrease. It is estimated that the electric capacity decreases when the amount of the negative electrode active material decreases. Further, when the amount of the solid electrolyte is reduced, it is considered that the ion conductivity of the negative electrode is lowered, the rate characteristics may be lowered, the utilization rate of the negative electrode active material is lowered, and the electric capacity may be lowered.

In order to tightly bind the negative electrode active material and the solid electrolyte to each other, a binder may be further included.
Binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), fluorine-containing resins such as fluorine rubber, thermoplastic resins such as polypropylene and polyethylene, ethylene-propylene-diene rubber (EPDM), and sulfonation. EPDM, natural butyl rubber (NBR) or the like can be used alone or as a mixture of two or more. In addition, an aqueous dispersion of cellulose or styrene butadiene rubber (SBR), which is an aqueous binder, can also be used.

The negative electrode mixture can be produced by mixing a solid electrolyte, a negative electrode active material, and an optional conductive additive and / or binder.
The mixing method is not particularly limited, but, for example, dry mixing using a mortar, ball mill, bead mill, jet mill, planetary ball mill, vibrating ball mill, sand mill, cutter mill; and mortar after dispersing the raw material in an organic solvent , Ball mill, bead mill, planetary ball mill, vibrating ball mill, sand mill, and wet mix, and then wet mixing to remove the solvent can be applied. Among these, wet mixing is preferable in order not to destroy the negative electrode active material particles.

-Positive electrode mixture A positive electrode mixture is obtained by mix | blending a positive electrode active material with the solid electrolyte of this invention.
The positive electrode active material is a material capable of inserting and removing lithium ions, and those known as positive electrode active materials in the battery field can be used. Moreover, the positive electrode active material developed in the future can also be used.

Examples of the positive electrode active material include metal oxides and sulfides. The sulfide includes a metal sulfide and a nonmetal sulfide.
The metal oxide is, for example, a transition metal oxide. Specifically, V ₂ O ₅ , V ₆ O ₁₃ , LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li (Ni _a Co _b Mn _c ) O ₂ (where 0 <a <1, 0 <b <1, 0 <c <1, a + b + c = 1), LiNi _1-Y Co _Y ₂ O ₂ , LiCo _1-Y Mn _Y ₂ O ₂ , LiNi _1-Y Mn _Y ₂ O ₂ (where 0 ≦ Y <1), Li (Ni _a Co _b Mn _c ) O ₄ (0 <a <2, 0 <b <2, 0 <c <2, a + b + c = 2), LiMn _2−Z Ni _Z O ₄ , LiMn _{2 —Z} Co _Z O ₄ (where 0 <Z <2), LiCoPO ₄ , LiFePO ₄ , CuO, Li (Ni _a Co _b Al _c ) O ₂ (where 0 <a <1, 0 <b < 1, 0 <c <1, a + b + c = 1) and the like.
Examples of the metal sulfide include titanium sulfide (TiS ₂ ), molybdenum sulfide (MoS ₂ ), iron sulfide (FeS, FeS ₂ ), copper sulfide (CuS), and nickel sulfide (Ni ₃ S ₂ ).
Other examples of the metal oxide include bismuth oxide (Bi ₂ O ₃ ) and bismuth leadate (Bi ₂ Pb ₂ O ₅ ).
Examples of non-metal sulfides include organic disulfide compounds and carbon sulfide compounds.
In addition to the above, niobium selenide (NbSe ₃ ), metal indium, and sulfur can also be used as the positive electrode active material.

The positive electrode mixture may further contain a conductive additive.
The conductive auxiliary agent is the same as the negative electrode mixture.

The blending ratio of the solid electrolyte and the positive electrode active material of the positive electrode mixture, the content of the conductive additive, and the method for producing the positive electrode mixture are the same as those of the negative electrode mixture described above.

[Lithium ion battery]
The lithium ion battery which concerns on one Embodiment of this invention contains at least 1 among the sulfide solid electrolyte and electrode compound material of this invention mentioned above. Or it manufactures with at least 1 among the sulfide solid electrolyte of this invention, and an electrode compound material.
The configuration of the lithium ion battery is not particularly limited, but generally has a structure in which a negative electrode layer, an electrolyte layer, and a positive electrode layer are laminated in this order. Hereinafter, each layer of the lithium ion battery will be described.

(1) Negative electrode layer The negative electrode layer is preferably a layer produced from the negative electrode mixture of one embodiment of the present invention.
Alternatively, the negative electrode layer is preferably a layer containing the negative electrode mixture of one embodiment of the present invention.
The thickness of the negative electrode layer is preferably from 100 nm to 5 mm, more preferably from 1 μm to 3 mm, and even more preferably from 5 μm to 1 mm.
A negative electrode layer can be manufactured by a well-known method, for example, can be manufactured by the apply | coating method and an electrostatic method (an electrostatic spray method, an electrostatic screen method, etc.).

(2) Electrolyte layer The electrolyte layer is a layer containing a solid electrolyte or a layer manufactured from a solid electrolyte. The solid electrolyte is not particularly limited, but is preferably the sulfide solid electrolyte of the present invention.
The electrolyte layer may consist only of a solid electrolyte, and may further contain a binder. As the binder, the same binder as that for the negative electrode mixture of the present invention can be used.

The thickness of the electrolyte layer is preferably 0.001 mm or more and 1 mm or less.
The solid electrolyte of the electrolyte layer may be fused. Fusion means that a part of the solid electrolyte particles is dissolved and the dissolved part is integrated with other solid electrolyte particles. The electrolyte layer may be a solid electrolyte plate, and the plate includes a case where a part or all of the solid electrolyte particles are dissolved to form a plate.
The electrolyte layer can be manufactured by a known method, and can be manufactured by, for example, a coating method or an electrostatic method (an electrostatic spray method, an electrostatic screen method, or the like).

(3) Positive electrode layer A positive electrode layer is a layer containing a positive electrode active material, Preferably it is a layer containing the positive electrode compound material of this invention, or the layer manufactured from the positive electrode compound material of this invention.
The thickness of the positive electrode layer is preferably 0.01 mm or more and 10 mm or less.
A positive electrode layer can be manufactured by a well-known method, for example, can be manufactured by the apply | coating method and an electrostatic method (an electrostatic spray method, an electrostatic screen method, etc.).

(4) Current collector The lithium ion battery of the present embodiment preferably further includes a current collector. For example, the negative electrode current collector is provided on the side of the negative electrode layer opposite to the electrolyte layer side, and the positive electrode current collector is provided on the side of the positive electrode layer opposite to the electrolyte layer side.
As the current collector, a plate or foil made of copper, magnesium, stainless steel, titanium, iron, cobalt, nickel, zinc, aluminum, germanium, indium, lithium, or an alloy thereof can be used.

The lithium ion battery of this embodiment can be manufactured by bonding and joining the above-described members. As a method of joining, there are a method of laminating each member, pressurizing and pressure bonding, a method of pressing through two rolls (roll to roll), and the like.
Moreover, you may join to the joining surface through the active material which has ion conductivity, and the adhesive material which does not inhibit ion conductivity.
In joining, heat fusion may be performed as long as the crystal structure of the solid electrolyte does not change.
Moreover, the lithium ion battery of this embodiment can be manufactured also by forming each member mentioned above sequentially. It can be manufactured by a known method, for example, it can be manufactured by a coating method or an electrostatic method (electrostatic spray method, electrostatic screen method, etc.).

Hereinafter, the present invention will be described in more detail with reference to examples.
The evaluation method is as follows.
(1) Ion conductivity measurement and electronic conductivity measurement The sulfide solid electrolyte produced in each example was filled in a tablet molding machine, and a pressure of 407 MPa (press display value 22 MPa) was applied using a mini-press machine. did. Carbon was placed on both sides of the molded body as an electrode, and pressure was again applied with a tablet molding machine to prepare a molded body for measurement (diameter of about 10 mm, thickness of 0.1 to 0.2 cm). The ion conductivity of this molded body was measured by AC impedance measurement. The value at 25 ° C. was adopted as the value of ionic conductivity.
Note that the ion conductivity measurement method used in this example cannot be measured because the ion conductivity cannot be accurately measured when the ion conductivity is less than 1.0 × 10 ⁻⁶ S / cm. It was.
Further, the electronic conductivity of this molded body was measured by direct current electric measurement. The value at 25 ° C. was used for the value of electron conductivity. When the electron conductivity when a voltage of 5 V was applied was less than 1.0 × 10 ⁻⁶ S / cm, the electron conductivity was not measurable.

(2) X-ray diffraction (XRD) measurement A circular pellet having a diameter of 10 mm and a height of 0.1 to 0.3 cm was formed from the sulfide solid electrolyte powder produced in each example to prepare a sample. This sample was measured using an airtight holder for XRD without being exposed to air. The 2θ position of the diffraction peak was determined by the centroid method using the XRD analysis program JADE.
The measurement was performed under the following conditions using a powder X-ray diffraction measurement device SmartLab manufactured by Rigaku Corporation.
Tube voltage: 45kV
Tube current: 200 mA
X-ray wavelength: Cu-Kα ray (1.5418mm)
Optical system: Parallel beam method Slit configuration: Solar slit 5 °, entrance slit 1 mm, light receiving slit 1 mm
Detector: Scintillation counter Measurement range: 2θ = 10-60deg
Step width, scan speed: 0.02 deg, 1 deg / min

In the analysis of the peak position for confirming the existence of the crystal structure from the measurement result, the XRD analysis program JADE was used, and the peak position was obtained by subtracting the baseline by cubic approximation.
In terms of peak intensity, one peak intensity of the argilodite type crystal structure existing at 2θ = 29.7 deg ± 0.5 deg, Li ₃ existing at 2θ = 17.6 ± 0.4 deg and 18.1 ± 0.4 deg. The two peak intensities of the PS ₄ crystal structure were analyzed by the following procedure, and the intensity ratio was calculated.

Smoothing was performed by moving average of five points of measured data, and the lowest intensity point between 17.5 and 18.5 deg was subtracted from the measured data as a background. Thereafter, the maximum value of the actual measurement data between the maximum values of the actual measurement data of 17.0 to 17.8 deg and 17.9 to 18.5 deg is calculated, and the smaller peak intensity is the peak intensity of the Li ₃ PS ₄ crystal structure. Used as. In addition, the peak intensity of the aldilodite crystal structure was calculated using the maximum value of actually measured data of 29.0 to 32.0 deg as the peak intensity.

(3) ICP Measurement The sulfide solid electrolyte powder produced in each example was weighed and collected in a vial in an argon atmosphere. A KOH alkaline aqueous solution was placed in a vial, and the sample was dissolved while paying attention to the collection of sulfur, and diluted appropriately to obtain a measurement solution. This was measured with a Paschenrunge type ICP-OES apparatus (SPECTRO ARCOS manufactured by SPECTRO) to determine the composition.
For the calibration curve solution, Li, P, S, Ge, Si are 1000 mg / L standard solution for ICP measurement, Cl, Br are 1000 mg / L standard solution for ion chromatography, and I is potassium iodide (special grade reagent). Prepared.
Two measurement solutions were prepared for each sample, five measurements were performed on each measurement solution, and an average value was calculated. The composition was determined by averaging the measured values of the two measurement solutions.

Production Example 1
(Production of lithium sulfide (Li ₂ S))
A 500 mL separable flask equipped with a stirrer was charged with 200 g of LiOH anhydride (manufactured by Honjo Chemical Co., Ltd.) dried under an inert gas. The temperature was raised under a nitrogen stream, and the internal temperature was maintained at 200 ° C. Nitrogen gas was switched to hydrogen sulfide gas (Sumitomo Seika), the flow rate was 500 mL / min, and LiOH anhydride and hydrogen sulfide were reacted.
Water generated by the reaction was condensed and collected by a condenser. When the reaction was performed for 6 hours, 144 mL of water was recovered. The reaction was further continued for 3 hours, but no generation of water was observed.
The product powder was collected and measured for purity and XRD. As a result, the purity was 98.5%, and a peak pattern of Li ₂ S was confirmed by XRD.

Example 1
Lithium sulfide (purity 98.5%), diphosphorus pentasulfide (manufactured by Thermophos, purity 99.9% or more), lithium chloride (manufactured by Sigma-Aldrich, purity 99%) and lithium bromide (produced in Production Example 1) Sigma Aldrich, purity 99%) was used as a starting material (hereinafter, the purity of each starting material is the same in all examples). The molar ratio of lithium sulfide (Li ₂ S), diphosphorus pentasulfide (P ₂ S ₅ ), lithium chloride (LiCl) and lithium bromide (LiBr) (Li ₂ S: P ₂ S ₅ : LiCl: LiBr) is 47. Each raw material was mixed so as to be 5: 12.5: 30: 10. Specifically, 0.461 g of lithium sulfide, 0.587 g of diphosphorus pentasulfide, 0.269 g of lithium chloride, and 0.183 g of lithium bromide were mixed to obtain a raw material mixture.

The raw material mixture and 30 g of zirconia balls having a diameter of 10 mm were placed in a planetary ball mill (Fritsch Co., Ltd .: Model No. P-7) zirconia pot (45 mL) and completely sealed. The inside of the pot was an argon atmosphere. Processing was performed for 48 hours (mechanical milling) at a rotational speed of 370 rpm with a planetary ball mill to obtain a glassy powder (intermediate).

About 1.5 g of the above intermediate powder is packed in a Tamman tube (PT2, manufactured by Tokyo Glass Equipment Co., Ltd.) in a glove box under an Ar atmosphere, and the mouth of the Tamman tube is closed with quartz wool. The container was sealed to prevent air from entering. Thereafter, the sealed container was placed in an electric furnace (FUW243PA, manufactured by Advantech) and heat-treated. Specifically, the temperature was raised from room temperature to 500 ° C. at a rate of 2.5 ° C./min (heated to 500 ° C. over 3 hours) and held at 500 ° C. for 10 hours. Thereafter, it was gradually cooled to obtain a sulfide solid electrolyte.

The ionic conductivity (σ) of the sulfide solid electrolyte was 7.9 mS / cm. The electron conductivity was less than 10 ⁻⁶ S / cm.
The XRD pattern of the sulfide solid electrolyte is shown in FIG. At 2θ = 15.4, 17.8, 25.4, 29.9, 31.3, 44.9, 47.8, and 52.3 deg, peaks derived from the aldilodite crystal structure were observed. On the other hand, no peak derived from the Li ₃ PS ₄ crystal structure was observed.
The sulfide solid electrolyte was analyzed by ICP and the molar ratio of each element was measured. Further, the ionic conductivity σ was measured. The results are shown in Table 1.

Examples 2 to 15 and Comparative Example 1
A sulfide solid electrolyte was produced and evaluated in the same manner as in Example 1 except that the raw material composition and production conditions were changed as shown in Table 2. The results are shown in Table 1.
Note that the electronic conductivity of any sulfide solid electrolyte was less than 10 ⁻⁶ S / cm. Further, as a result of the XRD measurement, a peak derived from the aldilodite type crystal structure was observed.
The XRD pattern of the sulfide solid electrolyte obtained in Example 4 is shown in FIG. Peaks derived from the aldilodite crystal structure were observed at 2θ = 15.4, 17.8, 25.4, 29.9, 31.3, 44.9, 47.7, and 52.3.

Example 16
An intermediate was produced in the same manner as in Example 1 except that the raw material composition and production conditions were changed as shown in Table 2.
In a glove box under an Ar atmosphere, about 1.5 g of the intermediate powder was packed in a glass tube with a sealing function, and the tip of the glass tube was sealed with a special jig so that air did not enter. Thereafter, the glass tube was set in an electric furnace. A dedicated jig was inserted into a joint in the electric furnace, connected to a gas flow pipe, and heat treated while flowing hydrogen sulfide at 0.5 L / min. Specifically, the temperature was raised from room temperature to 500 ° C. at 3 ° C./min and held at 500 ° C. for 4 hours. Thereafter, it was gradually cooled to obtain a sulfide solid electrolyte.
The obtained sulfide solid electrolyte was evaluated in the same manner as in Example 1. The results are shown in Table 1. The sulfide solid electrolyte obtained in Example 16 also had an electron conductivity of less than 10 ⁻⁶ S / cm. Further, as a result of the XRD measurement, a peak derived from the aldilodite type crystal structure was observed.

Example 17
In Example 17, kneading using a biaxial kneader was performed instead of the MM treatment of Example 1 for the production of the intermediate. Specifically, the kneading using the biaxial kneader was performed as follows.
A feeder (manufactured by Aisin Nano Technologies, Microfeeder) and a twin-screw kneading extruder (manufactured by Kurimoto Iron Works, KRC kneader, paddle diameter φ8 mm) were installed in the glove box. A mixture of 1.447 g of LiCl, 1.779 g of LiBr, 2.980 g of Li ₂ S, and 3.794 g of P ₂ S ₅ was supplied at a constant speed from the supply unit by a feeder, and the rotation speed was 150 rpm and the temperature was 250 ° C. The kneading was carried out by measuring the outer surface of the casing of the biaxial kneading extruder with a thermometer. In about 120 minutes, the powder was discharged from the kneader outlet. The operation of returning the discharged powder to the supply section again and kneading was repeated 5 times. The total reaction time was about 10 hours.
The obtained intermediate was heat treated at 430 ° C. for 4 hours in the same manner as in Example 1 to obtain a sulfide solid electrolyte.

The obtained sulfide solid electrolyte was evaluated in the same manner as in Example 1. The results are shown in Table 1.
The sulfide solid electrolyte obtained in Example 17 had an electron conductivity of less than 10 ⁻⁶ S / cm. Further, as a result of the XRD measurement, a peak derived from the aldilodite type crystal structure was observed.

Example 18
A sulfide solid electrolyte was produced using a biaxial kneader in the same manner as in Example 17 except that the raw material composition and production conditions were changed as shown in Table 2, and evaluated in the same manner as in Example 1. The results are shown in Table 1.
The sulfide solid electrolyte obtained in Example 18 had an electron conductivity of less than 10 ⁻⁶ S / cm. Further, as a result of the XRD measurement, a peak derived from the aldilodite type crystal structure was observed.

For the sulfide solid electrolytes produced in Examples 11 to 18 and Comparative Example 1, the peak intensity ratio of the lithium halide and Li ₃ PS ₄ crystal structure peaks in XRD was measured. The results are shown in Table 3.

In Table 3, _{I B} is the diffraction peak intensity of 2θ = 25.2 ± 0.5deg, _{I A} is (intensity of the diffraction peak of LiCl) intensity of the diffraction peak of 2θ = 50.3 ± 0.5deg with 2 [Theta] = The sum of the diffraction peak intensities of 46.7 ± 0.5 deg (the intensity of the LiBr diffraction peak). I _C is the intensity of the diffraction peak of 2θ = 17.6 ± 0.4 deg and 2θ = 18.1 ± 0.4 deg, although it is not a diffraction peak due to the argilodite type crystal structure. _ID is the intensity of the diffraction peak at 2θ = 29.7 ± 0.5 deg.

Examples 19 to 44 Comparative Examples 2 to 6
A sulfide solid electrolyte was produced and evaluated in the same manner as in Example 1 except that the raw material composition and production conditions were changed as shown in Table 4 or Table 6. The results are shown in Table 5 or Table 7.
Note that the electronic conductivity of any sulfide solid electrolyte was less than 10 ⁻⁶ S / cm. Further, as a result of the XRD measurement, a peak derived from the aldilodite type crystal structure was observed.

Example 45
The lithium sulfide, phosphorous pentasulfide, lithium chloride and lithium bromide used in Example 1 and lithium iodide (LiI: Sigma-Aldrich, purity 99%) were used as starting materials. Each raw material was mixed so that the molar ratio (Li ₂ S: P ₂ S ₅ : LiCl: LiBr: LiI) was 47.5: 12.5: 25.0: 12.5: 2.5. Specifically, 0.440 g of lithium sulfide, 0.560 g of diphosphorus pentasulfide, 0.214 g of lithium chloride, 0.219 g of lithium bromide, and 0.067 g of lithium iodide were mixed to obtain a raw material mixture.
A sulfide solid electrolyte was produced in the same manner as in Example 19 except that the raw material mixture was changed.
The σ of the sulfide solid electrolyte was 11.0 mS / cm. The electron conductivity was less than 10 ⁻⁶ S / cm.
As a result of the XRD measurement, a peak derived from the aldilodite type crystal structure was observed.
As a result of ICP analysis, the molar ratio b (S / P) was 4.3, the molar ratio c ((Cl + Br + I) / P) was 1.6, and c / b was 0.37.

Example 46
The lithium sulfide, diphosphorus pentasulfide, lithium chloride, and lithium bromide used in Example 1 and germanium (IV) sulfide (GeS ₂ : manufactured by High-Purity Science Laboratory Co., Ltd., purity 99%) were used as starting materials. Each raw material was mixed so that the molar ratio (Li ₂ S: P ₂ S ₅ : GeS ₂ : LiCl: LiBr) was 46.9: 11.1: 2.5: 24.7: 14.8. Specifically, 0.443 g of lithium sulfide, 0.508 g of diphosphorus pentasulfide, 0.069 g of germanium (IV) sulfide, 0.215 g of lithium chloride, and 0.264 g of lithium bromide were mixed to obtain a raw material mixture.
A sulfide solid electrolyte was produced in the same manner as in Example 19 except that the raw material mixture was changed.
The σ of the sulfide solid electrolyte was 9.8 mS / cm. The electron conductivity was less than 10 ⁻⁶ S / cm.
As a result of the XRD measurement, a peak derived from the aldilodite type crystal structure was observed.
As a result of ICP analysis, the molar ratio b (S / (P + Ge)) was 4.3, the molar ratio c ((Cl + Br) / (P + Ge)) was 1.6, and c / b was 0.37.

Example 47
The lithium sulfide, diphosphorus pentasulfide, lithium chloride and lithium bromide used in Example 1 and silicon disulfide (SiS ₂ : manufactured by High Purity Science Laboratory Co., Ltd.) were used as starting materials. Each raw material was mixed so that the molar ratio (Li ₂ S: P ₂ S ₅ : SiS ₂ : LiCl: LiBr) was 46.9: 11.1: 2.5: 24.7: 14.8. Specifically, 0.450 g of lithium sulfide, 0.515 g of diphosphorus pentasulfide, 0.048 g of silicon disulfide, 0.218 g of lithium chloride, and 0.269 g of lithium bromide were mixed to obtain a raw material mixture.
A sulfide solid electrolyte was produced in the same manner as in Example 19 except that the raw material mixture was changed.
The σ of the sulfide solid electrolyte was 7.5 mS / cm. The electron conductivity was less than 10 ⁻⁶ S / cm.
As a result of the XRD measurement, a peak derived from the aldilodite type crystal structure was observed.
As a result of ICP analysis, the molar ratio b (S / (P + Si)) was 5.2, the molar ratio c ((Cl + Br) / (P + Si)) was 1.6, and c / b was 0.31.

[Hydrogen sulfide generation amount of sulfide solid electrolyte]
The amount of hydrogen sulfide generated in the sulfide solid electrolyte produced in Example 13, Example 36, and Comparative Example 2 was evaluated using the apparatus shown in FIG. This apparatus includes a flask 1 for humidifying air, a flask 2 equipped with a temperature / humidity meter 6 for measuring the temperature and humidity of the humidified air, a Schlenk bottle 3 into which a measurement sample 4 is charged, and A hydrogen sulfide measuring instrument 7 for measuring the concentration of hydrogen sulfide contained is connected through a pipe in this order. The evaluation procedure is as follows.
About 0.1 g of a powder sample prepared by pulverizing the sample well in a mortar in a nitrogen glow box with a dew point of −80 ° C. was weighed and put into the 100 ml Schlenk bottle 3 and sealed (numbering in FIG. 5). 4).
Next, air was flowed into the flask 1 at 500 mL / min. The flow rate of air was measured with a flow meter 5. The flask 1 was humidified by passing air through it. Subsequently, humidified air was introduced into the flask 2 and the temperature and humidity of the air were measured. The temperature of the air immediately after the start of distribution was 25 ° C., and the humidity was 80 to 90%. Then, humidified air was circulated in the Schlenk bottle 3 and brought into contact with the measurement sample 4. The humidified air circulated through the Schlenk bottle 3 was passed through a hydrogen sulfide measuring instrument 7 (Model 3000RS manufactured by AMI), and the amount of hydrogen sulfide contained in the humidified air was measured. The measurement time was from immediately after air circulation to 1 hour after circulation. The amount of hydrogen sulfide was recorded at intervals of 15 seconds.
From the total amount of hydrogen sulfide observed over 2 hours, the amount of hydrogen sulfide generated per gram of the sample (mg / g) was calculated. As a result, the sulfide solid electrolyte of Example 13 was 26 mg / g, the sulfide solid electrolyte of Example 36 was 14 mg / g, and the sulfide solid electrolyte of Comparative Example 2 was 64 mg / g.

[Lithium ion battery]
Using the sulfide solid electrolyte obtained in Example 13 and Comparative Example 1, a lithium ion battery was manufactured and rate characteristics were evaluated.

(A) Manufacture of Lithium Ion Battery 50 mg of the sulfide solid electrolyte obtained in Example 13 or Comparative Example 1 was put into a stainless steel mold having a diameter of 10 mm, leveled flat, and the thickness of the electrolyte layer was even. After that, pressure was formed by applying a pressure of 185 MPa from the upper surface of the electrolyte layer with a hydraulic press.
Li ₄ Ti ₅ O ₁₂ coated LiNi _0.8 Co _0.15 Al _0.05 O ₂ as the positive electrode active material, and the sulfide solid electrolyte obtained in Example 13 or Comparative Example 1 as the solid electrolyte was 70:30 by weight. The positive electrode material 15 mg was added to the upper surface of the electrolyte layer and leveled flatly so that the thickness of the positive electrode layer was uniform, and then 407 MPa from the upper surface of the positive electrode layer with a hydraulic press. Pressure molding was performed by applying pressure.
The negative electrode active material graphite powder and the sulfide solid electrolyte obtained in Example 13 or Comparative Example 1 were mixed at a weight ratio of 60:40 to obtain a negative electrode material. After 12 mg of negative electrode material was added to the surface of the electrolyte layer opposite to the positive electrode layer and leveled flat so that the negative electrode layer had a uniform thickness, a pressure of 555 MPa was applied from the upper surface of the negative electrode layer with a hydraulic press. Was added and pressure-molded to prepare a lithium ion battery having a three-layer structure of a positive electrode, a solid electrolyte layer, and a negative electrode.

(B) Rate characteristic test The lithium ion battery produced in the above (A) was evaluated after being allowed to stand in a thermostatic bath set at 25 ° C for 12 hours. Charged to 4.2 V at 0.1 C (0.189 mA) in the first cycle, discharged to 3.1 V at 0.1 C (0.189 mA) and 4 at 0.5 C (0.945 mA) from 2 to 10 cycles The battery was charged to 2 V and discharged to 0.5 C (0.945 mA) 3.1 V. The capacity at the 10th cycle was measured. Using a lithium ion battery manufactured separately using the same sample, the capacity at the 10th cycle when charging and discharging at 1 C to 10 cycles at 0.1 C was measured. The ratio of the capacity when charging / discharging at 0.5 C and the capacity when charging / discharging at 0.1 C was taken as the evaluation value of the rate characteristics. The rate characteristic of the lithium ion battery using the sulfide solid electrolyte of Example 13 was 73%. In the lithium ion battery using the sulfide solid electrolyte of Comparative Example 1, it was 50%.

Although several embodiments and / or examples of the present invention have been described in detail above, those skilled in the art will appreciate that these exemplary embodiments and / or embodiments are substantially without departing from the novel teachings and advantages of the present invention. It is easy to make many changes to the embodiment. Accordingly, many of these modifications are within the scope of the present invention.
All the contents of the Japanese application specification that is the basis of the priority of Paris in this application are incorporated herein.

Claims

Lithium, phosphorus, sulfur,
Two or more elements X selected from halogen elements,
Including argilodite-type crystal structure,
A sulfide solid electrolyte in which the molar ratio b (S / P) of sulfur to phosphorus and the molar ratio c (X / P) of element X to phosphorus satisfy the following formula (1).
0.23 <c / b <0.57 (1)
The sulfide solid electrolyte according to claim 1, wherein a molar ratio b (S / P) of sulfur to phosphorus and a molar ratio c (X / P) of element X to phosphorus satisfy the following formula (1a).
0.25 ≦ c / b ≦ 0.43 (1a)
The sulfide solid electrolyte according to claim 1, wherein a molar ratio b (S / P) of sulfur to phosphorus and a molar ratio c (X / P) of element X to phosphorus satisfy the following formula (1b).
0.30 ≦ c / b ≦ 0.41 (1b)
The sulfide solid electrolyte according to any one of claims 1 to 3, wherein at least one of the elements X is chlorine.
The sulfide solid electrolyte of Claim 4 which satisfy | fills following formula (2).
0.25 <X Cl <1 (2)
(Wherein X 1 Cl represents a molar ratio of the chlorine to the element X)
6. The sulfide solid electrolyte according to claim 1, which has diffraction peaks at 2θ = 25.2 ± 0.5 deg and 29.7 ± 0.5 deg in powder X-ray diffraction using CuKα rays.
The sulfide solid electrolyte according to any one of claims 1 to 6, wherein at least one of the elements X is bromine.
The molar ratio a (Li / P) of the lithium to the phosphorus, the molar ratio b (S / P) of the sulfur to the phosphorus, and the molar ratio c (X / P) of the element X to the phosphorus are represented by the following formula ( The sulfide solid electrolyte according to any one of claims 1 to 7, which satisfies A) to (C).
5.0 ≦ a ≦ 7.5 (A)
6.5 ≦ a + c ≦ 7.5 (B)
0.5 ≦ ab ≦ 1.5 (C)
(In the formula, b> 0 and c> 0 are satisfied.)
The sulfide solid electrolyte according to any one of claims 1 to 8, which has a composition represented by the following formula (3).
Li a (P 1−α M α ) S b X c (3)
Wherein M is one or more elements selected from the group consisting of Si, Ge, Sn, Pb, B, Al, Ga, As, Sb and Bi, and X is F, Cl, Br and I Two or more elements selected from the group consisting of: a to c satisfy the following formulas (A) to (C), and α is 0 ≦ α ≦ 0.3.
5.0 ≦ a ≦ 7.5 (A)
6.5 ≦ a + c ≦ 7.5 (B)
0.5 ≦ ab ≦ 1.5 (C)
(In the formula, b> 0 and c> 0 are satisfied.)
An electrode mixture comprising the sulfide solid electrolyte according to any one of claims 1 to 9 and an active material.
A lithium ion battery comprising at least one of the sulfide solid electrolyte according to any one of claims 1 to 9 and the electrode mixture according to claim 10.
An electrode mixture produced from the sulfide solid electrolyte according to any one of claims 1 to 9.
A lithium ion battery manufactured from at least one of the sulfide solid electrolyte according to any one of claims 1 to 9, the electrode composite according to claim 10, and the electrode composite according to claim 12.